Dan K wrote:
It would appear the folks at Curtiss OD'ed the area first and then installed the glass (Or am I misunderstanding the question?).

You pegged it. Curtiss seems to have painted just that area first where as Republic painted the whole fuselage and then installed the canopy.
This photo of Zemke's P-47B suffers from being scanned from a postcard but it sure looks OD under the aft part of the canopy. There is a better quality shot in Warren Bodie's tome to the P-47 that is even clearer.

Same shot in B/W.

An another shot. When photographed where the lighjt is very direct it sure lookd OD to me.

Logic would indicate that the area behind the cockpit would be OD on camoed airplanes so as to not detract from camouflage. On a NMF there would be no need to paint it, though a few planes during that transition might have had OD, or chromate there.
WW II was a war of production as well as anything else. All efforts were made to mass produce weapons and vehicles were made. Nothing would have been gained by painting areas differently unless some sort of protection to the surface was needed. A good example was the G503 1/4 ton truck, otherwise known as the jeep. All jeeps were produced under Army Quatermaster Corps contracts, whether Willys MB or Ford GPW jeeps. They came out of the factory OD and it did not matter what service the ended up with. They were not painted gray for the Navy and a different green for the USMCs. Vehicles were simply send delivered from the QMC contract in a batch to other services as they came off the line. If that receiving service wished to waste time repainting any vehicles after delivery that was their choice.
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Had God intended for man to fly behind inline engines, Pratt & Whitney would have made them.
CB
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